According to the new Mechanistic Empirical Pavement Design Guide (MEPDG) and 1993 AASHTO flexible pavement design guide, Resilient Modulus (MR) has been used extensively as an important material property in structure design of pavement. The modulus is used as the primary input parameter to determine the stiffness parameters and constitutive behavior of pavement components. The system of pavement basically consists of the layers of surface, base, subbase (optional), and subgrade. The compacted subgrade soils supporting pavement structure are typically unsaturated with degrees of saturation varying from 75% to 90%. The effect of unsaturated soil behavior on the mechanical properties of compacted pavement materials become an important variable and need to be considered. The main purpose of this study is to study the resilient moduli properties of compacted and unsaturated subgrade materials and to determine the effect of compaction moisture content, which is related to matric suction of the soils, on the resilient moduli properties. The second objective is to study the use of MEPDG models to calibrate resilient moduli properties either as a function of moisture content or soil suction variables. To accomplish these objectives, soil specimens were prepared at five different moisture content and dry density conditions and tested using conventional resilient modulus testing as per AASHTO T-307 procedure. The basic soil tests such as grain size distribution, Atterberg's limits, and standard proctor compaction were initially performed. Then, the advanced soil tests consisting of soil water characteristic curve (SWCCs), unconfined compressive strength (UCS) test, and conventional resilient modulus test were conducted. The soil suction conditions of the prepared specimens were determined based on the SWCCs information and the compaction moisture content. The test results indicate that compaction moisture content affected the values of resilient modulus of the subgrade soils. The specimens compacted at dry side of optimum moisture content (OMC) showed higher values of resilient modulus compared with the specimens compacted at OMC and wet side of OMC. The testing data were also analyzed with the models provided in MEPDG program. The level 2 input for predicting SWCCs provided in MEPDG gave the predicted SWCCs in similar trend to the measured SWCCs. However, the curves were not quite well matched. Lastly, the modified universal model and the model proposed by Cary and Zapata (2010) were studied and analyzed in detail. The results showed that the universal model is well suited for predicting the resilient modulus of the subgrade soils. However, the resilient modulus values predicted by the model of Cary and Zapata, sometime, showed the higher values than measured results especially, the specimens compacted at 0.8OMC.

A pavement system basically consists of a surface layer, a base course, a subbase (optional) and the subgrade. As per MEPDG and 1993 AASHTO flexible pavement design guide Resilient Modulus (MR) is used as the primary input parameter to determine the stiffness parameters and the constitutive behavior of pavement components, such as subgrade and unbound bases. Generally, pavements are constructed on compacted soils that are typically unsaturated with degrees of saturation varying from 75 to 90%. The main focus of this research is to determine the effect of matric suction on the resilient moduli property of the base materials. The second objective of the research is to study the use of MEPDG models to calibrate resilient moduli properties either as a function of moisture content or soil suction variables. In order to assess these objectives, these unbound materials were tested using suction controlled MR and moisture controlled MR procedures. Amendments were done by preparing the specimens at five different moisture content and dry density conditions. Suction controlled MR testing took longer time to reach the equilibrium conditions and the results obtained were close to the results obtained from moisture controlled MR procedure. The initial suction conditions are studied using Fredlund device (Tempe cell). Test results indicate that the specimens compacted on the dry side of the optimum have high resilient modulus due to the stress hardening behavior. MEPDG program procedure was followed to predict the soil water characteristic curve. Lastly, two three model parameter models developed by Cary and Zapata (2010) and Modified Universal model are studied and analyzed in detail. Validity of the correlation equations are addressed by comparing measured MR to predicted MR values. Results suggest that the models used are well suited for predicting the resilient modulus and soil water characteristic curve of the two unbound base materials.

At head of title: National Cooperative Highway Research Program.

This book constitutes the proceedings of the First International Conference on Emerging Trends in Engineering (ICETE), held at University College of Engineering and organised by the Alumni Association, University College of Engineering, Osmania University, in Hyderabad, India on 22–23 March 2019. The proceedings of the ICETE are published in three volumes, covering seven areas: Biomedical, Civil, Computer Science, Electrical & Electronics, Electronics & Communication, Mechanical, and Mining Engineering. The 215 peer-reviewed papers from around the globe present the latest state-of-the-art research, and are useful to postgraduate students, researchers, academics and industry engineers working in the respective fields. This volume presents state-of-the-art, technical contributions in the areas of civil, mechanical and mining engineering, discussing sustainable developments in fields such as water resource engineering, structural engineering, geotechnical and transportation engineering, mining engineering, production and industrial engineering, thermal engineering, design engineering, and production engineering.

The objectives of this research are to establish a resilient modulus test results database and to develop correlations for estimating the resilient modulus of Wisconsin fine-grained soils from basic soil properties. A laboratory testing program was conducted on representative Wisconsin fine-grained soils to evaluate their physical and compaction properties. The resilient modulus of the investigated soils was determined from the repeated load triaxial (RLT) test following the AASHTO T307 procedure. The laboratory testing program produced a high-quality and consistent test results database.